The present project's objectives are first, to isolate rat colonic epithelial cells from the other cell populations that exist in this organ. Second, to isolate mitotically active and inactive fractions of these epithelial cells from different regions of the rat colon. Third, to isolate luminal and contraluminal membranes from these cells and characterize them biochemically. Fourth, to then treat animals with 1,2 dimethylhydrazine and isolate and characterize these membranes. Fifth, to compare normal and "abnormal" plasma membranes for differences in their biochemical composition.